The subject matter disclosed herein relates to a fault detection system system, and more specifically to a fault detection system including a generator and a power converter that is selectively connected to the generator.
Wind turbines are one alternative to conventional sources of energy. A wind turbine includes multiple blades that are connected to a rotor, where spinning of the blades by wind spins a shaft of the rotor. The rotor is connected to a generator that generates electricity. Some wind turbines include a gearbox that couples the rotor to the generator. Various types of generators are employed in wind turbines such as, for example, induction machines and separately excited synchronous machines. Specifically, one type of generator that may be employed is a permanent magnet generator. The permanent magnet generator allows for higher efficiency but, because the permanent magnet generator is excited by permanent magnets, the permanent magnet generator is almost always capable of producing voltage when spinning Thus, as long as the permanent magnet generator is spinning, voltage will typically be produced. However, a fault may occur on the output of the permanent magnet generator while voltage is being produced. Thus, a breaker may be provided to the output of the generator to generally prevent the current flow in the event of a fault.
A power converter system may also be employed to convert the variable frequency electrical output power of the generator to an AC electrical power that matches the frequency of an electrical grid. Sometimes the power converter is not activated. For example, the power converter may not be activated if there is not adequate wind, maintenance work is being performed on the wind turbine, or in the event the wind turbine is nonoperational.
A fault may occur between the cables that connect the generator to the power converter. For example, the fault may be a short or an open circuit. In the event the power converter is activated, detection of a fault between the generator and the power converter is typically relatively simple to detect. While operating, both the power converter and the breakers an internal trip relay will detect the fault. The power converter will shut down and the breaker will open. However, in the event the power converter is not activated, this fault may go undetected. When a generator breaker is in a closed position, the power converter may or may not be activated. One approach for detecting a fault between the generator and the power converter when the power converter is not activated but the breaker is closed involves employing an internal trip relay in the generator main circuit breaker. However, the internal trip relay may not always be reliable at lower frequencies, and may also be prone to overheating while the power converter is activated due to the current harmonics produced by the power converter.